1. Field of the Invention
The present invention relates to a container of a structure in which a seaming curl portion or a seaming flange portion is partially cut or notched, and to a lid body used therewith and a method of seaming a container.
2. Description of Related Art
Such a kind of conventional seamed container has a structure as shown in FIG. 5, for example.
That is, a seaming curl portion 121 protruding or hanging over the periphery of a lid body 120 is put on a seaming flange portion 111 formed at an open end portion of a container body 110, so that the seaming curl portion 121 and the seaming flange portion 111 are seamed together to be joined to each other by means of a seaming roll 130.
The seaming curl portion 121 extends in an outward direction through a chuck wall portion 123 which rises from the periphery of a panel 122, as shown in (C) and (D) in FIG. 5, and at the time of seaming, an inner periphery of the chuck wall portion 123 is pushed or pressed down by a chuck 140, and the chuck 140 receives a pressing force due to the seaming roll 130 through the chuck wall portion 123.
However, in cases where a notch 150 is formed in the seaming curl portion 121 in advance so as to form a partial opening in a seam portion of a container in a manner as illustrated, a stress concentrates on the vicinity of the notch 150, which is easy to cause abnormal deformation. In particular, in the case of the container having a polygonal or square shape, as shown in (C) in FIG. 5, seam shaping is simple bending shaping in a straight line region L between corner portions, but becomes draw forming in a corner portion C, as a result of which, though the pressing force due to the seaming roll 130 is supported by the chuck 140, the force acting on a straight line region between the corner C and an adjacent next corner portion beyond the corner portion C becomes large, so that when the notch 150 exists in this portion, a stress concentrates on the vicinity of the notch 150, thus giving rise to a problem of buckling and caving in.
A seaming structure of a container having such a notch 150 is described in the following first and second patent documents, for example.